1. Field of the Invention
The invention relates generally to test instrumentation and more particularly to test simulators for infrared wavelength devices, wherein black body radiators having known thermal radiation intensity are used as a test signal source for infrared imaging and tracking systems test and evaluation. In particular, the invention relates to a thermal imaging means that is relatively inexpensive compared with the prior art by using a novel matrix technical approach to the problem.
An example of a one dimensional thermal source is the popular Fax machine. As a linear thermal source is heated, a thermal paper senses the heat and makes a black spot at the location of the print element; after one scan the paper is moved to the next line and the printed lines are integrated to form a letter or picture.
If this FAX machine-like source would be combined with a scanning mirror and observed by an Infrared camera, a moving object thermal image could be displayed; if a low temperature background is required, the imaging source, mirrors and observation camera must be mounted in a high vacuum tank and cooled to cryogenic temperature. Such a system becomes very expensive. Also, the simple fax machine-like mechanism could not withstand thermal cycling.
There is a need for a relatively inexpensive two-dimensional thermal imaging source capable of operation in a cryogenic environment for generating movable images formed and controlled by computer.
2. Description of the Prior Art
Prior art Black Body radiation sources have been used as thermal standards but were fixed in position. No provision for movement was made. Later, a prior art system was created using scanning mirrors for one degree, or for two degrees of freedom, to create a moving target. However, more than two objects, and independent relative motion cannot be simulated by this system. Also, if a low temperature background source is required, the mirror system, and camera, must be included in a high vacuum tank and cooled to cryogenic temperature. A prior art system of this type using mirrors exists and is very expensive and functionally limited. A black-body matrix using transistors to trigger the thermal elements on and off was used and was prohibitively expensive as well as performance limited.